Low flow conversion burner



Jan. 6, 1970 o, A. DAVIS ET AL 3, 8

LOW FLOW CONVERSION BURNER Filed April 19 INVENTORS.

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United States Patent 3,488,134 LOW FLOW CONVERSION BURNER Orvis A. Davis, Gibsonia, and Bruce R. Walsh, Pittsburgh, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Apr. 19, 1968, Ser. No. 722,738 Int. Cl. F2341 17/00 U.S. Cl. 431-171 12 Claims ABSTRACT OF THE DISCLOSURE The invention comprises a low heat output by-pass nozzle burner particularly suited for converting water heaters and the like from gas firing to oil firing. The apparatus is a compact, self-contained unit including a nested fuel pump and air shutter in the space Within a squirrel cage blower.

This invention relates to the art of oil burners, and more particularly it is directed to a burner apparatus for converting low heat requirement installations to fuel oil burning from other fuels.

The apparatus of the invention comprises a compact, self-contained conversion or replacement burner particularly adapted to convert gas-fired water heaters to oil firing. The invention is also useful in other like applications such as small heaters for use in house trailers, summer air conditioners, and other applications that will suggest themselves to those skilled in this art.

The advantages of the invention flow from its relatively small physical size and its relatively low fuel capacity. The low fuel capacity is obtained by employing a by-pass nozzle, i.e., a nozzle which passes a portion of the fuel supplied to it to the combustion area and which bypasses the remainder of the fuel back to supply. The burner of the invention can have a relatively small capacity on the order of .3 gallon per hour.

The apparatus comprises a number of individual features which in combination result in the compact burner of the invention with all its attendant advantages. One of these features is the utilization of a squirrel cage blower. The space within this blower, which is wasted in many other prior apparatuses, is utilized to house the fuel pump, and other parts. Means are provided to interconnect the shafts of the fuel pump, the blower, and the drive motor, at one location inside the blower. Another feature comprises a self-contained combustion chamber defined by an insulated open top box on the outer end of the air blast tube, with means at the top opening to create a back pressure therein to contain the flame and improve combustion. In certain applications, the box need not be insulated.

Still another feature is the combustion head and swirl plate, which cooperates with the combustion chamber to assure clean continuous combustion. Absent the particular swirl plate and combustion head, improper combustion would result, in that the flame, which is closely contained by the combustion chamber, would not burn properly therein.

Because of its relatively, small physical size and low fuel flow capability, the apparatus of the invention is highly versatile as to types of installations in which it may be used to convert to oil burning. This versatility is further enhanced by another feature comprising an ad justable adapter plate of suitable size and shape mounted on the blast tube to cover the opening in the water heater or other installation in which the burner is inserted.

The above and other advantages of the invention will be pointed out or will become evident in the following detailed description and claims, and in the accompanying drawing also forming a part of the disclosure, in which:

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FIG. 1 is a top plan view of the apparatus of the invention with some parts broken away and some parts in cross-section; FIGS. 2, 3, and 4 are cross-sectional views on lines 2-2, 33, and 44 of FIG. 1 respectively; FIG. 5 is a cross-sectional view of the nozzle; and FIG. 6 is an enlarged view of a nozzle detail.

Referring to the drawing, 10 designates a conversion oil burner embodying the invention. Burner 10 comprises a main central housing 12 made up of an imperforate right side wall 14, a left side wall 16, and a curved scroll shaped outer wall 18 interconnecting walls 14 and 16. Main housing 12 is of more or less the usual configuration for gun type oil burners, with the bottom outlet end of the scroll described by wall 18, and with the blast tube assembly 20 connected to said outlet.

Within housing 12 is a squirrel cage type blower 22 which operates in the usual manner, drawing air from the inside and forcing it through its blades and to the outside. Blower 22 comprises a central hub 24, one annular face of which carries a pair of drive pins 26, see FIG. 2, which are received within suitably formed openings in a coupling disk 28. Disk 28 is formed with a second pair of openings, offset from the openings receiving pins 26 by which receive a pair of drive pins 30 formed on a drive member 32. Drive member 32 receives the shaft 34 of a high pressure fuel pump 36. The shaft 38 of the main drive motor 40 is received within the central opening in fan hub 24. Thus, the motor, the fan, and the fuel pump 36 are interconnected at the area of coupling disk 28 in a compact manner and entirely in the space within fan 22. Disk 28 is preferably fabricated of leather, hard rubber, or other suitable flexible material. Motor 40 is held in place on the right wall 14 of housing 12 by a central support 39, which encloses the motor shaft 38, and by a plurality of suitable outrigger supports 41.

Left wall 16 is formed with a central opening large enough to permit physical passage of the fan 22 therethrough for assembly and general service purposes. This opening is closed oif by a relatively thick plate member 42 held in place by any suitable means, not shown. Means are provided to adjust the amount of air drawn in by fan 22 and supplied for combustion. To this end, a sliding, circular plates air shutter assembly 44 is provided, with its outer end secured by suitable means in the central opening in plate member 42. Shutter assembly 44 includes a control arm 46 which extends out through scroll shaped wall 18 for manual adjustment of the shutter in the usual manner. The air shutter is housed substantially entirely within the space within the fan 22. The fuel pump 36 passes through the circular end wall of the shutter assembly 44, and it too is substantially entirely housed within the fan 22. Suitable sealing means are provided between the plate member 42 and the shutter assembly 44, and between pump 36 and shutter 44, so that all the air supplied to the fan must pass through the controlled openings provided by air shutter 44.

Fuel pump 36 is a commercial item available from the Tuthill Pump Company of Chicago, Ill., their model number 5-10. It has a capacity of about 7 g.p.h., at about p.s.i. It is of the type that by-passes part of the fuel back to the source of fuel, and supplies the remainder of the fuel to the nozzle under pressure. Fuel enters the pump 36 through a pair of input fittings 48 which interconnect the fuel inlet port of the pump to a pipe 50 running from the outlet side of a fuel filter 52. A pipe 54, only a portion of which is shown, connects the by-pass port of the pump back to the fuel supply in any suitable manner. A fitting 56 interconnects the pressurized output port of the pump to a pipe 58 which runs to the input of the nozzle, as will appear more clearly below.

Mounted on plate member 42, outboard of the opening in which shutter 44 is mounted, is a pair of vertically disposed structural members 60 which carry a transformer and the associated electrical components 62 required for the electrical and ignition systems. Means are provided to move transformer and electrical components 62 to permit access to the remaining components housed within main housing 12. To this end, one support 60 carries a hinge 64 about which transformer 62 may swing, and the other support carries a suitable tightening nut or other securing means 66 to hold the transformer in the operative posi tion. At its inner side, transformer 62 comprises a pair of connection members 68 to which the ignition leads are connected, as will appear in more detail below.

As mentioned briefly above, means are provided to filter the fuel before it is supplied to the nozzle for combustion. Fuel filter 52 may be of any suitable commercial type and comprises an inlet fitting 70 at its lower end, to which a fuel supply pipe 72, from a suitable tank or other point of supply not shown, is connected. The fuel pipe 50, running from the filter 52 to the fuel pump 36, is connected to the filter adjacent its upper end.

Connected to the outlet end of main housing 12 is an air supply or blast tube 20, which comprises an outwardly flaring rear portion 74 attached to the main housing 12 to adapt to the change in cross-sectional shape, and a main body portion 76. Adjustably mounted on main body portion 76 is an adapter shield 78 comprising a face plate portion 80 and a cylindrical portion 82 adapted to snugly fit around body 76. Securing means 84 is provided in cylindrical portion 82 to hold adapter shield 78 in adjusted position thereon. A hose, clamp or other suitable means may be used. Shield 78 is most useful where a water heater built to burn gas is being converted to burn oil. In such an application, after the burner is being converted to burn oil. In such an application, after the burner is positioned in the combustion space under the water tank, the shield is slid on the blast tube up against the opening in the bottom of the water heater. Plate portion 80 is trimmed to fit, if necessary, and secured in position, and then used to support other portions of the apparatus, such as electrical controls and the flame sensor forming part of the safety system, all not shown.

Mounted within the cylindrical body portion 76 of the blast tube 20 at its forward end is a combustion head apparatus 86. Combustion head 86 is of the general type of US. Patent No. 3,404,844, Ser. No. 556,339, filed June 9, 1966, by Bruce R. Walsh, entitled Oil Burner Combustion Head, and assigned to the same assignee as the present invention. Reference may be had to the above for a detailed description of this combustion head and its operation. However, generally, combustion head 86 comprises a front plate portion 88 which defines the exit orifice, a cylindrical portion 90 extending rearwardly from the edge of front portion 88 to snugly fit within the front end of the blast tube, and a conical wall portion 92 extending rearwardly and outwardly from the orifice in front plate 88 and terminating in an axial flange portion 94 having a diameter substantially equal to the inside diameter of the blast tube. Combustion head 86 also comprises a swirl plate 96 mounted within conical wall portion 92 at the rear end thereof adjacent flange 94. Thus, a swirl and mixing chamber 98 is defined by the front face of swirl plate 96 and conical wall portion 92 forward of the swirl plate. As shown in FIGS. 3 and 4, swirl plate 96 is formed with a pair of openings 100 which receive ignition means 102, usually in the form of high voltage electrodes. Electrical leads 104 connect the electrodes 102 to the electrical connectors 68 on transformer 62. The electrical, safety, control and ignition systems of the present invention are generally conventional and well known to those skilled in the art and may include suitable intermediary electrode support means 106 located in the blast tube. Swirl plate 96 is formed with a central opening 108, which receives the fuel nozzle 110.

Swirl plate 96 comprises four swirl slots each of which is defined by an edge cut-out portion in the swirl plate and that portion of conical wall 92 which overlies that cut-out. Means are provided to hold the swirl plate 96 in position in the combustion head 86. To this end, dimple holding means 97 are formed in the lands between the swirl slots in the swirl plate and by swagged or otherwise deformed and fitted portions in the axial flange 94, as shown. Any other suitable holding means may be employed.

The swirl slots 95 are relatively narrow, radially, and are relatively wide, circumferentially. This particular configuration of the swirl slots, in cooperation with the relatively confined, insulated space in the combustion chamber 114 produces eflicient combustion. The wide and thin swirl slots produce a relatively thin sheet of air confining the cone of flame issuing from the nozzle, which tends to shorten the flame when it passes into the space within the combustion chamber i114. Thus, the relatively small space in the combustion chamber is efliciently utilized with a minimum of heat wasted by being imparted to the insulation.

Combustion chamber 114 has the general shape of a rectangular box open at the top. It comprises a pair of side walls 116, a bottom wall 118, a front end wall 120, and another end wall similar to wall 120. End wall is formed with an orifice 122 having a diameter substantially equal to the exit diameter in front plate portion 88 of combustion head 86. Combustion chamber 114 comprises a cylindrical sleeve 124 which snugly fits over blast tube portion 76 and includes securing means such as set screw 126. Means are provided to constrain or contain the flame within combustion chamber 114. To this end, the top opening of the combustion chamber is reduced by provision of a top corbel 128 fitted closely around the tops of the sides and ends of the combustion chamber. Corbel 128 comprises a lower flange portion 130 that fits snugly against the side and end walls and is held in place by any suitable means such as spot welding, and an upper flange portion 132 extending upwardly and inwardly from the region of said top and end walls. All inside surfaces, with the exception of the region of orifice 122, and including upper flange portion 132 of the corbel 128, may be insulated by a layer 134 of suitable heat insulation material. The insulation may comprise asbestos sheeting, or the like.

The burner of the invention may be used with virtually any liquid fuel, the nozzle being chosen to suit the fuel, of course. As shown, the apparatus will burn the economical and commercially popular #2 ASTM grade fuel oil.

Referring to FIGS. 5 and 6, nozzle 110 comprises a central swirl stern formed with a plurality of swirl slots 142 which are disposed on an angle to the axis of and on the truncated conical face of the swirl stem, all in the usual manner. A through return or by-pass opening 146, of predetermined diameter, extends rearwardly from the front face 144 of the swirl stem.

Extending rearwardly of the front of the swirl stem 140 is a return line tubing portion 148. In spaced relation to its front end, tubing 148 is formed with a segmented male threaded portion 150 that cooperates with a female threaded portion 152 formed on the inside of the main nozzle housing 154. The rear end of the main housing 154 is formed with external screw threads 156 which cooperate with suitably formed threads on a fuel supply conduit 158. Adapter 112 cooperates with return tubing 148 and supply conduit 158 to separate the flows in these two conduit portions in a known manner, not shown. Supply conduit 158 is connected to pipe 58 and a pipe 160 is connected to return tubing 148, both via adapter 112. Pipe 160 carries the by-passed fuel and air back to a point of supply, not shown.

Means are provided to form a swirl chamber in front of the swirl stem 140. To this end, an orifice disk or nib 162 is positioned against the truncated conical face of the swirl stem, extends therefrom forwardly of front face 144, and terminates in an exit orifice 164 of predetermined diameter. Orifice disk 162 is held tightly in position by the interaction of threads 152 with threaded segments 150, and by suitably formed interengaging cut-outs and shoulders on the front of the housing 154 and on the exterior of the nib 162. The housing 154 extends forwardly of exit orifice 164 in the orifice disk, and is provided with an exit orifice 166 and a plurality of radial air passages 168. Passages 168 supply air that envelopes the outside of the spray cone issuing from orifice 164 through orifice 166.

Referring to FIG. 6, the operation of bypass nozzle 110 is illustrated. The oil is supplied under pressure through supply conduit 158, passes through the annular space between the inside of the main housing 154 and the outside of the return tubing 148, longitudinally between the segmented threaded portions 150, and out the swirl slots 142. Upon exiting from the slots 142, the fuel forms a swirling sheet on the inside surface of the orifice disk or nib 162. By providing a relatively small diameter exit orifice 164, this sheet of fuel is caused to thicken at its entrance end. By providing a by-pass opening 146 of a diameter larger than the diameter of exit orifice 164, a portion of the fuel supplied through the swirl slots 142 will return through the by-pass opening 146 in the form of a froth. The air which froths the returning fuel enters through the center of the cone or tube of fuel formed when the swirling sheet of fuel exits from orifice 164.

The swirling fuel in the swirl chamber creates a low pressure vortex at its center. This vortex has been used in the past to draw fluids into itself from the rear, rather than to draw air into itself from the front as shown in FIG. 6. This prior arrangement is shown in US. Patent No. 2,948,478 of Bruce R. Walsh assigned to the same assignee as the present invention. However, in the above mentioned prior nozzle, the orifice analogous to orifice 164 is larger than the opening analogous to opening 146. By providing that the exit orifice shall be smaller than the return or by-pass opening, the condition wherein air will be drawn rearwardly from inside the cone of fuel droplets into the swirl chamber vortex and thence into the by-pass passageway is assured. The amount of fuel bypassed can be controlled by suitable adjustable restricting means such as a valve, not shown, in the return pipe 160.

By way of example, a 100 p.s.i. nozzle nominally rated forone gallon per hour was modified to provide a return opening 146 having a diameter of about .013 inch and an exit orifice of about .008 inch. By use of a valve in line 160 it was possible to achieve a flow out of the nozzle for combustion ranging from the full one g.p.h. (wherein the return valve was closed), down to an effective flow as small as .27 g.p.h., which means that about 73% of the fuel supplied was by-passed.

While the invention has been described in detail above, it is to be understood that this detailed description is by way of example only, and the protection granted is to be limited only within the spirit of the invention and the scope of the following claims.

We claim:

1. In an oil burner, the combination comprising a housing, a squirrel cage blower in said housing, said housing comprising a pair of side walls, air inlet means mounted on one of said pair of side Walls, said air inlet means extending inwardly from said one of said pair of side walls into the space within said blower, fuel pump means comprising an input drive shaft mounted on said one of said pair of side walls and extending through said air inlet means and into the space within said blower, said fuel pump means being located at least mounted on the other of said pair of side walls comprising an output drive shaft, said blower comprising a drive hub located in the space within said blower; and

connection means located in the space Within said blower directly interconnecting said blower hub, said motor output drive shaft, and said fuel pump means input drive shaft.

2. The combination of claim 1, said connection means comprising a drive member mounted on said fuel pump means input drive shaft having a pair of drive pins extending therefrom, said blower hub being of toroidal shape and comprising a pair of annular faces, said motor output drive shaft being operatively connected to the central opening of said blower hub, one of said annular faces of said blower hub being connected to said blower and the other of said annular faces comprising a pair of drive pins extending therefrom, and said connection means comprising a coupling disk interconnecting said drive pins of said drive member and said drive pins of said blower hub.

3. The combination of claim 2, said coupling disk consisting of leather.

4. The combination of claim 1, said air inlet means comprising a sliding, circular plates air shutter assembly and manual control means for said assembly, whereby the amount of air supplied by said air inlet means for combustion can be manually adjusted.

5. The combination of claim 1, an air blast tube extending outwardly of said housing, a fuel nozzle at the outlet end of said blast tube, means to supply fuel under pressure from said fuel pump means to said nozzle, and means to by-pass a portion of the fuel supplied to said nozzle back to the fuel source.

6. The combination of claim 5, said fuel pump means supplying fuel at a rate in the range of about .27 g.p.h. to about 1.00 g.p.h. and at about p.s.i.

7. The combination of claim 5, a combustion head at the outlet end of said blast tube, said combustion head comprising an outlet end exit orifice, means forming a truncated conical swirl chamber extending inwardly of said exit orifice, swirl means at the entrance end of said swirl chamber, and the exit end of said nozzle being positioned in said swirl chamber.

8. The combination of claim 7, said swirl means comprising a swirl plate formed with a plurality of swirl slots extending inwardly from the periphery thereof, each of said swirl slots having a radial dimension substantially smaller than its circumferential dimension, and the total circumferential measurement of all of said swirl slots together at the periphery of said swirl plate being larger than the total circumferential measurement of the lands between said swirl slots at the periphery of said swirl plate.

9. The combination of claim 5, said oil burner being adapted to convert a water heater from gas firing to oil firing, and an adapter shield adjustably mounted on said blast tube, whereby said adapter shield may be moved on said blast tube to cover the access opening in a water heater after the water heater has been converted to oil burning.

10. The combination of claim 8, said swirl plate being formed with four swirl slots each having a circumferential measurement at least two and a half times the circumferential measurement of each of said lands between said swirl slots, whereby said swirl plate produces a relatively thin sheet of swirling air.

11. The combination of claim 1, an air blast tube extending outwardly of said housing, a combustion chamber removably mounted at the outlet end of said blast tube, said combustion chamber having the shape of a rectangular box open at the top, and a flame containing corbel at the upper open end of said combustion chamber comprising an upwardly and inwardly sloped wall on all four sides of said combustion chamber.

12. In combination, a blower housing, a squirrel cage blower in said housing, a drive motor comprising an output drive shaft, a fuel oil pump mounted substantially within said blower and comprising an input drive shaft,

air shutter means housed in the space within said blower adapted to control the flow of air supplied to said blower, connection means housed in the space within said blower drivingly interconnecting said blower, said output drive shaft, and said pump input drive shaft, a blast tube extending from said blower housing, means forming a swirl chamber at the outlet end of said blast tube, an oil nozzle having its outlet end positioned in said swirl chamber, a combustion chamber removably mounted at the outlet end of said blast tube and extending outwardly thereof, and said combustion chamber comprising flame containing means at an open side thereof; whereby the assembly of said blower, said nozzle, said swirl means, and said combustion chamber may be used as a unit to convert an installation to oil burning from other fuels.

References Cited UNITED STATES PATENTS Huff 431-171 X Andler 239-406 Jorolemom 431-171 Halliman 431-183 Greenland 239-125 Fiske et al 431-183 De Lancey 431-265 X EDWARD G. FAVORS, Primary Examiner U.S. Cl. X.R.

3 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,488, 134 Dated January 6, 1970 I Orvis A. Davis, Bruce R. Walsh It is certified that: error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

F A whole line has been left out at column 5 between lines 72 and 73. The omitted line should read --partly in the space within said blower, drive motor means--.

Column 3, lines 35 and 36, the following words shoulx be deleted, such words appearing correctly in the following lines: In such an application, after the burner is being converted to burn oil."

SIGNED fiND SEALED SEAL) Arrest:

Edward M. Fletcher, In,

WILLIAM E. 'SGIIUYLER, JR. Investing Officer Commissioner of Patents 

